\documentclass[10pt,oneside]{book}

\input{macros_orig.tex}

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\begin{document}

\pagestyle{empty}
\thispagestyle{empty}

\begin{codebox}
  \Procname{$\proc{Cross-Validate}(\data, k)$}
  \li divide $\data$ into $k$ chunks $\data_1, \data_2, \ldots \data_k$ (of roughly equal size)
  \li \For $i \gets 1$ \To $k$
  \li   \Do
          train $h_i$ on $\data \setminus \data_i$ (withholding chunk $\data_i$)
  \li     compute ``test'' error $\mathcal{E}_i (h_i)$ on withheld data $\data_i$
        \End
  \li \Return $\frac{1}{k} \sum_{i=1}^k \mathcal{E}_i (h_i)$
\end{codebox}

\end{document}
